Suppression of synaptic plasticity by cerebrospinal fluid from anti-NMDA receptor encephalitis patients.

The functional effects of cerebrospinal fluid (CSF) from patients with anti-NMDA receptor (NMDAR) encephalitis on the NMDAR-mediated synaptic plasticity were evaluated by using mouse hippocampus slices. Anti-NMDAR antibody detection system was established by immunostaining recombinant NMDAR heteromers expressed in HEK cell culture as well as native NMDARs in cultured hippocampal neurons. Under a complete blind manner for the clinical information, CSF and sera collected from 36 pre-diagnosed patients were tested for anti-NMDAR antibodies. With this test, thirteen patients were diagnosed as anti-NMDAR encephalitis. CSF positive for anti-NMDAR antibodies suppressed induction of long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in mouse hippocampal slices. LTP induction was not suppressed by CSF collected from herpes simplex virus (HSV) encephalitis or non-encephalitis control patients. Antibody absorption with NMDAR-expressing HEK cell culture reversed the suppression of LTP by anti-NMDAR encephalitis patients' CSF, confirming that anti-NMDAR antibodies suppressed LTP. The present experiments firmly support the proposal that the anti-NMDAR encephalitis autoantibody is responsible for cognitive disorders like amnesia accompanying this disease.